“To follow those waters … which will henceforth lead us into strange lands.”

The “…” isn’t mine. It belongs to the four bronze plates of French voyageurs endlessly exploring the Dearborn Street entryway to the Marquette Building downtown. The reddish, soot-stained terra cotta office building is a dwarf among the glass giants of the Loop. It’s outshone. Purely and plainly, passersby’s eyes either draw to the modernist glass-and-steel and whorling cherry-red steel sculptures of Federal Plaza to the south or to the distant Art Institute to the east, the latter a sign that their tourist trek from Union Station is almost at an end.

It’s nice. It’s cool and fine, sort of an “Oh, that’s charming!” from the outside.

But there’s a secret.

The 10-story Montauk building, opened in 1883 and torn down in 1902, was the first to be called “skyscraper,” but it wasn’t substantially different from other buildings. It used cast-iron columns and wrought-iron floor beams, sure, but it still had exterior load-bearing walls, just like the rest. It wasn’t until 1885 that Chicago’s Home Insurance Building taught the world a thin skeleton of iron and steel could hold up 10 stories of stone and businessmen. Architect William Le Baron Jenney, his partner would later write, was inspired in part by childhood memories of the thin braces of wood he saw Filipino men mesh and weave into sturdy houses during a three-month trip to Manila on his father’s New Bedford whaling ship.

The Marquette, with its red terra cotta and the four bronze panels of early French trappers promising to follow waters to strange lands, was part of the building boom that followed. It’s from 1895 and was designed by the firm of Holabird & Roche. Successor firm Holabird & Root today has its offices on the fifth floor. The building’s skeleton was modeled after Home Insurance; its location spurred by the clock tower train station you can see if you look due south and have excellent vision.

From 7 a.m. to 10 p.m., seven days a week, the Marquette lobby and a small architecture exhibit in the next room are free and open to the public. Go in. Go through one of the revolving doors engraved with the bronze kickplates of the “altogether mysterious calumet” peace pipe the chief of the Illinois presented early missionary Father Jacques Marquette as a token of friendship.

(Less romantic is the fact it was a secondary gift, with the main gift being “a little slave,” and that the calumet was a gift “upon which they place more value than upon a slave,” Marquette wrote.)

Find yourself in one of the most beautiful foyers Chicago offers.

To each side, marble staircases swooping to the second of the two stories of bronze and colored glass that make up the entryway. The Tiffany glass mosaics circling the walls depicts the early days of what would become Chicago and the French trappers, traders and missionaries who were the first non-Native people to pass through the area. All but two of the 22 bronze portraits over the two levels of elevators were done by Edward Kemeys, the sculptor of the lions outside the Art Institute of Chicago. Amy Aldis Bradley sculpted the other two: Marquette and fur trapper Louis Jolliet, who led the 1673 expedition shown in glass on the lobby and bronze outside and who are considered the first non-Native Americans to explore the region. One per elevator, the portraits depict individual European explorers alongside individual Native American residents, a rare touch of identity sculpted in an era when Natives who graced works of art were depicted as interchangeable savages. Here instead they are mixed among the whites, implying through the scatter that what was about to happen was consensual and equal.

This isn’t the secret.

The building is known. It’s a tourist mainstay — in the summer months a conga line of walking tours dance in and out of those revolving doors to the annoyance of the now-quite-historically-versed security guards. It’s appeared in daffy movies and is a mainstay on the Architecture Foundation’s yearly Open House.

The gorgeous glass of the lobby hidden inside the drab red exterior isn’t the secret, any more than the steel skeleton hidden in the walls is. The secret is that everything started here. The mosaics show our history, from the French canoes that first explored these waters to, on the north wall, the tile face of Jolliet, the man who first suggested the canal that would build this vibrant, decaying, gorgeous and glowing city.

The secret of the Marquette is in those first few words — and the … — on the walls outside. In glass and bronze, the building immortalizes those waters. We are the strange lands.